Radical polymerization processes for preparing halogenated polymers, and halogenated polymers

ABSTRACT

Radical polymerization process for the preparation of halogenated polymers employing one or more ethylenically unsaturated monomers, at least one of which is chosen from halogenated monomers, molecular iodine and one or more radical-generating agents chosen from diazo compounds, peroxides and dialkyl diphenylalkanes Radical polymerization process for the preparation, starting from the halogenated polymers prepared by the process as described above, of block copolymers, at least one block of which is a halogenated polymer block. Halogenated polymers which have a number-average molecular mass Mn of greater than 1.0×10 4  and an Mz/Mw ratio of less than 1.65. Block copolymers, at least one block of which is a block of halogenated polymer identical to the halogenated polymers described above. Block copolymers comprising at least one halogenated polymer block which have a number-average molecular mass Mn of greater than 1.5×10 4  and a polydispersity index Mw/Mn of less than 1.60.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation Application of 11/431,836, filed May11, 2006, now U.S. Pat. No. 7,208,558, which is a ContinuationApplication of 10/512,870, filed Nov. 16, 2004, now U.S. Pat. No.7,078,473, which is a 371 of International Application PCT/EP03/05314,filed May 16, 2003, and claims priority to French application no.0206246, each of which is incorporated herein by reference in itsentirety.

The present invention relates to radical polymerization processes forthe preparation of halogenated polymers and to polymers, to thepreparation of which the polymerization processes which are a subjectmatter are particularly well suited.

Halogenated polymers are usually prepared according to a “conventional”radical polymerization process with the involvement of a halogenatedmonomer and of an agent which generates radicals, which initiates thegrowth of the polymer chains. According to this process, the timenecessary for a polymer chain to grow until it reaches its final size isvery short, often less than one second. Also, throughout the duration ofa polymerization, new chains are born, grow and “die” virtuallyimmediately by recombination, by disproportionation or by radicaltransfer. This “death” has a statistical, random, nature; it depends inparticular on the polymerization temperature and on the viscosity of themedium. In that way, at the end of the polymerization, a halogenatedpolymer is obtained which has a randomly spaced molecular massdistribution, the polydispersity index (M_(w)/M_(n)) and the M_(z)/M_(w)ratio of which have values usually of at least 2. Such a process doesnot make it possible to synthesize polymers having a narrow andcontrolled molecular mass distribution. Neither does it make it possibleto manufacture block copolymers.

Admittedly, halogenated polymers prepared by the abovementioned processare valued because they exhibit several advantageous properties, inparticular high chemical resistance to alkalis and to alcohols and highflame retardency. More particularly, the vinyl chloride polymersprepared by the abovementioned process are valued because they can, ifneed be, be rendered flexible by blending with plasticizers in order tomanufacture flexible articles, such as imitation leather.

However, they exhibit a number of weak points, the main one being thatthe numerous properties of these polymers which depend on the molecularmass are heterogeneous at the molecular scale, this being because theseproperties can vary from one polymer chain to another in the same way asthe molecular mass itself. In particular, the presence of polymer chainsof very low molecular mass within the halogenated polymers of the priorart substantially reduces their thermal stability; it also substantiallydamages the mechanical properties of the articles manufactured startingfrom the latter, in particular their tensile strength, abrasionresistance and scratching resistance. Conversely, the presence ofpolymer chains of very high molecular mass within these same halogenatedpolymers makes it more difficult to process them (higher meltviscosity); it also substantially damages the mechanical properties ofthe plasticized articles manufactured stating from the latter, due tolack of gelling (imperfect blending, at the molecular level, of thehalogenated polymer and of the plasticizer), and other properties ofthese articles, such as the transparency and the surface finish.

An attempt has already been made to overcome the disadvantages of theabovementioned “conventional” radical polymerization process and theweak points of the halogenated resins prepared by this process bydeveloping a polymerization process disclosed in patent application EP617 057 A. This process involves, in addition to the halogenated monomerand the radical-generating agent involved in the conventional process,an iodinated organic transfer agent comprising at least one iodine atombonded to a primary carbon atom, such as 1-chloro-1-iodoethane. It“apes”, according to the actual terms employed in this patentapplication, an “ideal” living radical polymerization process in thesense that, as is shown in example 4 of the abovementioned patentapplication, the number-average (or weight-average) molecular mass ofthe halogenated polymers synthesized by this process increases as thehalogenated polymer is polymerized. However, the polydispersity indexand the M_(z)/M_(w) ratio of the halogenated polymers synthesized bythis process, although lower than those of the halogentated polymersprepared by the conventional process, remain high (for example,polydispersity index of greater than or equal to 1.70 for vinyl chloridehomopolymers), which shows that the process in question is stronglyaffected by side reactions, just like the conventional process, bytransfer and/or disproportionation and/or recombination reactions whichinterrupt or halt the growth of the polymer chains. Another disadvantageof this process of the prior art is the need to employ an iodinatedorganic transfer agent, which is generally expensive and increases thecost price of the halogenated polymer.

The development of a process for the radical polymerization ofhalogenated monomers which is more effective than the processes of theprior art appeared to a person skilled in the art to be a particularlydifficult problem as halogenated monomers, in particular vinyl chloride,vinyl fluoride, vinylidene chloride and vinylidene fluoride, wereregarded as intrinsically inclined to transfer the radical activity ofthe growing polymer chains onto themselves (reactions for transfer ontomonomer) and/or onto dead polymer chains (reactions for transfer ontopolymer).

A subject matter of the present invention is consequently first of all aradical polymerization process for the preparation of halogenatedpolymers which does not exhibit the disadvantages of the processes ofthe prior art while retaining their advantages.

To this end, the invention relates to a radical polymerization processfor the preparation of halogenated polymers employing

-   (A) one or more ethylenically unsaturated monomers, at least one of    which is chosen from halogenated monomers,-   (B) molecular iodine, and-   (C) one or more radical-generating agents chosen from diazo    compounds, peroxides and dialkyldiphenylalkanes,    which comprises the stages according to which-   (1) at least a fraction of each of the compounds (A), (B) and (C) is    introduced into a reactor, then-   (2) the contents of the reactor are reacted, while introducing    therein the optional balance of each of the compounds (A), (B) and    (C).

The term “halogenated polymers” is understood to denote bothhomopolymers of halogenated monomers and the copolymers which thehalogenated monomers form with one another or with nonhalogenatedmonomers. These copolymers can in particular be random copolymers, blockcopolymers or grafted copolymers.

The term “halogenated monomer” is understood to denote any ethylenicallyunsaturated monomer which comprises at least one halogen atom. Mentionmay be made, as examples of halogenated monomers, of halogenated vinylmonomers, halogenated styrene monomers, such as 4-bromostyrene,halogenated (meth)acrylic monomers, such as trifluoroethyl acrylate, andhalogenated conjugated dienes, such as chloroprene.

Advantageously, at least 50 mol % and preferably at least 75 mol %of-(A) are composed of one or more ethylenically unsaturated monomerschosen from halogenated monomers.

The halogenated monomers are preferably halogenated vinyl monomers. Theterm “halogenated vinyl monomers” is understood to denotemonoethylenically unsaturated halogenated monomers which are aliphaticand which have, as sole heteroatom(s), one or more halogen atoms.Mention may be made, as examples of halogenated vinyl monomers, ofbrominated vinyl monomers, such as vinyl bromide, fluorinated vinylmonomers and chlorinated vinyl monomers.

The halogenated monomers are particularly preferably chosen fromchlorinated vinyl monomers and fluorinated vinyl monomers.

The term “chlorinated vinyl monomers” is understood to denotemonoethylenically unsaturated chlorinated monomers which are aliphaticand which have, as sole heteroatom(s), one or more chlorine atoms.Mention may be made, as examples of chlorinated vinyl monomers, ofchlorinated vinyl monomers for which the number of chlorine atoms is 1,chlorinated vinyl monomers for which the number of chlorine atoms is 2,trichloroethylene, 1,1,3-trichloropropene and tetrachloroethylene.

A first preferred family of chlorinated vinyl monomers is composed ofchlorinated vinyl monomers for which the number of chlorine atoms is 1.Mention may be made, as examples of chlorinated vinyl monomers for whichthe number of chlorine atoms is 1, of allyl chloride, crotyl chlorideand, with a very particular mention, vinyl chloride.

A second preferred family of chlorinated vinyl monomers is composed ofchlorinated vinyl monomers for which the number of chlorine atoms is 2.Mention may be made, as examples of chlorinated vinyl monomers for whichthe number of chlorine atoms is 2, of 1,1-dichloropropene,1,3-dichloropropene, 2,3-dichloropropene and, with a very particularmention, vinylidene chloride.

The term “fluorinated vinyl monomers” is understood to denotemonoethylenically unsaturated fluorinated monomers which are aliphaticand which have, as sole heteroatom(s), one or more fluorine atoms andoptionally, in addition, one or more chlorine atoms. Mention may bemade, as examples of fluorinated vinyl monomers, ofchlorotrifluoroethyleene, trifluoroethylene, perfluorinated vinylmonomers, such as tetrafluoroethylene and hexafluoropropylene,fluorinated vinyl monomers devoid of chlorine atoms and for which thenumber of fluorine atoms is 1, and fluorinated vinyl monomers devoid ofchlorine atoms and for which the number of fluorine atoms is 2.

A first preferred family of fluorinated vinyl monomers is composed offluorinated vinyl monomers devoid of chlorine atoms and for which thenumber of fluorine atoms is 1. Mention may be made, as examples of suchmonomers, of allyl fluoride and, with a very particular mention, vinylfluoride.

A second preferred family of fluorinated vinyl Monomers is composed offluorinated vinyl monomers devoid of chlorine atoms and for which thenumber of fluorine atoms is 2. Mention may be made, as examples of suchmonomers, of 3,3,3-trifluoropropene and, with a very particular mention,vinylidene fluoride.

According to a first preferred alternative form of the radicalpolymerization process for the preparation of halogenated polymersaccording to the invention (alternative form (i)), (A) is composed of asingle ethylenically unsaturated monomer which is a halogenated monomer.

According to the alternative form (i), advantageously at least 50 mol %of (A) and preferably 100% of (A) are introduced into the reactor instage (1).

According to a second preferred alternative form of the radicalpolymerization process for the preparation of halogenated polymersaccording to the invention (alternative form (ii)), (A) is composed ofseveral ethylenically unsaturated monomners, at least one of which ischosen from halogenated monomers.

According to the alternative form (ii), (A) can optionally, in addition,comprise one or more nonhalogenated monomers.

If appropriate, the nonhalogenated monomers are preferably chosen fromstyrene monomers, such as styrene, (meth)acrylic monomers, such asn-butyl acrylate and methyl methacrylate, vinyl esters, such as vinylacetate, and olefinic monomers, such as ethylene, propylene andbutadiene.

According to the alternative form (ii), advantageously at least 25 mol %of (A) and preferably at least 50 mol % of (A) are introduced into thereactor in stage (1). Advantageously, at least 25 mol % and preferably100 mol % of the fraction of (A) introduced into the reactor in stage(1) are composed of one or more halogenated monomers.

According to the alternative form (ii), the respective policies forintroducing, into the reactor, the various ethylenically unsaturatedmonomers constituting (A), in stage (1) and in stage (2), can influencethe organization of the repeat units of the halogenated polymersproduced by the reaction.

According to a first preferred alternative subform of the alternativeform (ii) (alternative subform (ii.a)), the ethylenically unsaturatedmonomers constituting (A) are introduced into the reactor according tothe same introduction policy.

The halogenated polymers prepared according to the alternative subform(ii.a) are advantageously random copolymers.

According to a second preferred alternative subform of the alternativeform (ii) (alternative subform (ii.b)), one of the ethylenicallyunsaturated monomers constituting (A) is introduced into the reactor instage (1), the other ethylenically unsaturated monomer or monomersconstituting (A) being introduced into the reactor in stage (2), in asmany times as the number of ethylenically unsaturated monomersconstituting (A) minus 1, one after the other, each new introduction ofan ethylenically unsaturated monomer into the reactor in stage (2) beingcarried out only after the ethylenically unsaturated monomer or monomerspreviously introduced into the reactor has (have) each reacted up to atleast 50 mol %, particularly preferably at least 70 mol % and veryparticularly preferably at least 90 mol %.

The halogenated polymers prepared according to the alternative subform(ii.b) are advantageously copolymers, the molecular structure of whichis similar to but nevertheless different from that which ideal blockcopolymers exhibit (that is to say, without any interpenetration of theblocks).

According to a third preferred alternative subform of the alternativeform (ii) (alternative subform (ii.c)), one of the ethylenicallyunsaturated monomers constituting (A) [monomer (M₁)] is introduced intothe reactor in stage (1), all or a fraction of the other ethylenicallyunsaturated monomer or monomers constituting (A) [monomers (M₂)] beingintroduced gradually into the reactor in stage (2).

The optional fraction of the monomer or monomers (M₂) which has not beenintroduced gradually into the reactor in stage (2) is advantageouslyintroduced into the reactor in stage (1).

According to the alternative subform (ii.c), the monomer (M₂) or each ofthe monomers (M₂), if there are several of them advantageously has agreater reactivity than that of the monomer (M₁), that is to say thatthe overall rate at which the monomer (M₂) or each of the monomers (M₂)is consumed by the reaction is greater than that at which the monomer(M₁) is consumed. In addition, the rate of introduction of the monomer(M₂) or, if there are several of them, of each of the monomers (M₂) intothe reactor advantageously increases as the reactivity of this or thesemonomers increases.

The halogenated polymers prepared according to the alternative subform(ii.c) are advantageously copolymers, the molecular structure of whichis similar to that which ideal homogeneous copolymers exhibit (that isto say, all the polymer chains of which comprise exactly the same molarfraction of structural repeat units resulting from each of thecopolymerized monomers).

In the radical polymerization process for the preparation of halogenatedpolymers according to the invention, the molecular iodine (B) can beintroduced into the reactor as is or in the form of a precursor whichreacts in the reactor to release molecular iodine. Mention may be made,as examples of such precursors, of alkali metal iodides, such aspotassium iodide, provided that the reactor comprises an aqueous phaseat acidic pH with aqueous hydrogen peroxide solution or a water-solubleorganic peroxide. Preferably, (B) is introduced as is.

The number of moles of (B) with respect to the number of moles of (A)advantageously has a value of at least 2.5×10⁻⁵, preferably of at least5×10⁻⁵ and particularly preferably of at least 10⁻⁴. In addition, thenumber of moles of (B) with respect to the number of moles of (A)advantageously has a value of at most 10⁻¹ and preferably of at most10⁻².

Advantageously, at least 50 mol % of (B) and more advantageously still100% of (B) are introduced into the reactor before the duration of stage(2) has reached 2 hours, preferably before the duration of stage (2) hasreached 1 hour, and particularly preferably in stage (1).

The diazo compounds, the peroxides and the dialkylddiphenylalkaneschosen under (C) can be conventional.

Mention may be made, as examples of diazo compounds, of4,4′-azobis(4-cyanovaleric acid) (water-soluble diazo compound) andazobisisobutyronitrile (oil-soluble diazo compound).

Mention may be made, as-examples of peroxides, of water-solubleperoxides, such as ammonium persulfate and aqueous hydrogen peroxidesolution, and oil-soluble peroxides, such as dialkyl peroxides, dialkylperoxydicarbonates and peresters.

(C) is preferably oil-soluble.

The number of moles of (C) with respect to the number of moles of (B)advantageously has a value of at least 1. In addition, it advantageouslyhas a value of at most 10, preferably of at most 5.

Advantageously, at least 50 mol % of (C) and preferably 100% of (C) areintroduced into the reactor in stage (1).

In the radical polymerization process for the preparation of halogenatedpolymers according to the invention, it is optionally possible, inaddition, to introduce into the reactor, in stage (1) and/or in stage(2),

-   (D) one or-more complexes of a metal, in the 0 oxidation state or in    a strictly positive oxidation state, chosen from transition metals,    lanthanides, actinides and metals from Group IIIa, and of a ligand    of this metal.

According to a first embodiment of the radical polymerization processfor the preparation of halogenated polymers according to the invention(embodiment (I)), the following is additionally introduced into thereactor, in stage (1) and/or in stage (2),

-   (D) one or more complexes of a metal, in the 0 oxidation state or in    a strictly positive oxidation state, chosen from transition metals,    lanthanides, actinides and metals from Group IIIa, and of a ligand    of this metal.

Mention may in particular be made, as examples of metals in the 0oxidation state, of Al(0), Cr(0), Cu(0), Fe(0), Mg(0), Mo(0), Ni(0),Pb(0), Pd(0), Sm(0), W(0) and Zn(0).

Mention may in particular be made, as examples of metals in the strictlypositive oxidation state, of Ce(III), Cu(I), Cu(II), Fe(II), Fe(III),Ni(I), Rh(III), Rh(IV), Ru(III), Ru(IV) and Ti(IV). The metals in astrictly positive oxidation state are advantageously introduced in theform of salts, for example in the form of chlorides, of bromides, ofiodides or of tellurides.

The preferred metals are Cu(0), Cu(I), Cu(II) and Ti(IV).

Mention may in particular be made, as examples of ligands of theabovementioned metals, of amino ligands, such as bipyridine (Bpy) and1,1,4,7,10,10-hexamethyltriethylenetetramine, phosphorus-comprisingligands, such as triphenylphosphine (P(Ph)₃), and other ligands, such asindenyl, cyclopentadienyl (Cp), tris[2-aminoethyl]amine (TREN),tris[2-(dimethylamino)ethyl]amine (Me6TREN), and acetylacetonate andbutoxide (OBu) anions, where Bu denotes an n-butyl group.

The preferred ligands are (OBu)⁻, Cp, Bpy, TREN and Me6TREN.

Mention may in particular be made, as examples of complexes, ofCu(0)/Bpy, Cu(I)Cl/Bpy, Cu(I)Br/Bpy, Cu(I)I/Bpy, Cu(I)Cl/TREN,Cu(I)Cl/Me6TREN, Cu(II)Te/Bpy, Ti(IV)Cp₂Cl₂ and Ti(IV)(OBu)₄. Theabovementioned complexes have given very good results.

According to the embodiment (I), the number of moles of (D) with respectto the number of moles of (B) advantageously has a value of at least10³¹ ², preferably of at least 10⁻¹. In addition, it advantageouslyhas-a value of at most 10², preferably of at most 10¹.

According to the embodiment (I), the number of moles of (C) with respectto the number of moles of (B) advantageously has a value of at most 1.4and preferably of at most 1.2.

According to a second preferred embodiment of the radical polymerizationprocess for the preparation of halogenated polymers according to theinvention (embodiment (II)), the contents of the reactor, in stage (1)and in stage (2), are devoid of complex of a metal, in the 0 oxidationstate or in a strictly positive oxidation state, chosen from transitionmetals, lanthanides, actinides and metals from Group IIIa, and of aligand of this metal.

According to the embodiment (II), the number of moles of (C) withrespect to the number of moles of (B) advantageously has a value of atleast one 1.2 and preferably of at least 1.4.

The radical polymerization process for the preparation of halogenatedpolymers according to the invention can be in particular a solution,solution/bulk bulk, suspension, microsuspension or emulsionpolymerization process. Thus, in the radical polymerization process forthe preparation of halogenated polymers according to the invention, itis optionally possible to introduce into the reactor, in stage (1)and/or in stage (2), in addition to (A), (B), (C) and optionally (D), upto 1000% by weight, with respect to the weight of (A), of one or moreingredients conventionally employed to polymerize halogenated monomers,such as water, supercritical CO₂, liquid organic dispersants, such asisopropanol, organic solvents, such as benzene, tetrahydrofuran andcyclohexanone, dispersing agents, such as poly(vinyl alcohol)s, oremulsifying agents, such as ammonium myristate (ingredients (U)).

In order to bring about the reaction of the contents of the reactoraccording to stage (2), use is made of means by which radicals aregenerated within it. To this end, the contents can in particular beheated or can be exposed to intense light radiation.

The temperature at which the contents of the reactor are reactedadvantageously has a value of at least 30° C. and preferably of at least40° C. In addition, it advantageously has a value of at most 200° C. andpreferably of at most 120° C.

Advantageously, stage (2) is carried out until the halogenated monomeror monomers, on the one hand, and the optional nonhalogenated monomer ormonomers, on the other hand, have reacted within certain limits.

Thus, on the one hand, stage (2) is carried out until preferably atleast 10 mol % of the halogenated monomer or monomers introduced intothe reactor have reacted. In addition, stage (2) is carried out until(i) preferably at most 70 mol % and particularly preferably at most 35mol % of the halogenated monomer or monomers introduced into the reactorhave reacted, if the ethylenically unsaturated monomer or monomersintroduced into the reactor are exclusively chlorinated vinyl monomers,(ii) preferably at most 85 mol % and particularly preferably at most 70mol % of the halogenated monomer or monomers introduced into the reactorhave reacted, if the ethylenically unsaturated monomer or monomersintroduced into the reactor are exclusively halogenated monomers otherthan chlorinated vinyl monomers, and (iii) preferably at most 95 mol %of the halogenated monomer or monomers introduced into the reactor havereacted, if at least one ethylenically unsaturated monomer introducedinto the reactor is a nonhalogenated monomer.

On the other hand, stage (2) is carried out until preferably at least 50mol % of the optional nonhalogenated monomer or monomers introduced intothe reactor have reacted. In addition, stage (2) is carried out untilpreferably at most 95 mol % of the optional nonhalogenated monomer ormonomers introduced into the reactor have reacted.

To bring stage (2) to an end, it is possible, for example, to cool thecontents of the reactor and/or to introduce therein a powerfulinhibiting agent and/or to extract therefrom the fraction of (A) whichhas not reacted, it being possible for these operations to be carriedout simultaneously or successively, in the reactor or outside thelatter.

Preferably, stage (2) is brought to an end by extracting, from thecontents of the reactor, the fraction of (A) which is not reacted(demonomerization treatment), optionally after having cooled thecontents of the reactor and/or having introduced therein a powerfulinhibiting agent.

When the fraction of (A) which has not reacted has a sufficientvolatility, it will advantageously be extracted from the contents of thereactor by placing the latter under vacuum.

The radical polymerization process for the preparation of halogenatedpolymers according to the invention can, in addition, optionallycomprise a stage, subsequent to the preceding stages, according to whichthe halogenated polymer is isolated from the contents of the reactor(stage (3)).

Use may be made, to isolate the halogenated polymer from the contents ofthe reactor, of, in addition to the demonomerization treatment alreadydiscussed above, any separation technique known to a person skilled inthe art, in particular precipitation (especially when the halogenatedpolymer has been produced by a solution or solution/bulk process),filtering and drying in a fluidized bed (especially when the halogenatedpolymer has been produced by a suspension process), and drying byatomization or by coagulation (especially when the halogenated polymerhas been produced by an emulsion or microsuspension process). Theseoperations are advantageously carried out outside the reactor.

The radical polymerization process for the preparation of halogenatedpolymers according to the invention is advantageously carried out inorder to prepare the halogenated polymers according to the invention.

Subsequently, a subject matter of the present invention is a radicalpolymerization process for the preparation of block copolymers, at leastone block of which is a halogenated polymer block.

To this end, the invention relates to a radical polymerization processfor the preparation of block copolymers, at least one block of which isa halogenated polymer block, employing

-   (A′) one or more ethylenically unsaturated monomers, and-   (B′) one or more halogenated polymers chosen from the polymers    prepared by the process as described above and from those prepared    during a preliminary stage by the process concerned with here,    which comprises the stages according to which-   (1′) at least one fraction of (A′) and at least one fraction of (B′)    are introduced into a reactor, then-   (2′) the contents of the reactor are reacted, while introducing    therein the optional balance of (A′) and the optional balance of    (B′).

The radical polymerization process for the preparation of blockcopolymers according to the invention corresponds to the samecharacteristics and preferences as those described above regarding theradical polymerization process for the preparation of halogenatedpolymers, except for counterindication or unless it is otherwisespecified thereof.

The number of ethylenically unsaturated monomers constituting (A′) cantake any value, Preferably, it has a value of at most 2.

The ethylenically unsaturated monomer or monomers constituting (A′) canbe chosen without distinction from halogenated monomers andnonhalogenated monomers.

(B′) can be introduced into the reactor in any form whatsoever, inparticular in the form of a powder, of a dispersion, of an emulsion orof a solution, and after having or not having been isolated from thecontents of the reactor in which it was prepared beforehand. (B′) isintroduced into the reactor preferably after having been isolated fromthe contents of the reactor in which it was prepared beforehand.

The number of halogenated polymers constituting (B′) preferably has avalue 1.

Preferably, all of (B′) is introduced into the reactor in stage (1′).

The weight of (B′) with respect to the weight of (A′) advantageously hasa value of at least 0.1 and preferably of at least 0.5. In addition, itadvantageously has a value of at most 4.

In the radical polymerization process according to the invention, (C′)one or more radical-generating agents chosen from peroxides, diazocompounds and dialkyldiphenylalkanes is/are, in addition, advantageouslyintroduced into the reactor in stage (1′) and/or in stage (2′).

(C′) corresponds to the same characteristics and to the same preferencesas (C), this being the case whatever the degree of preference.

In the radical polymerization process for the preparation of blockcopolymers according to the invention, (D′) one or more complexes of ametal, in the 0 oxidation state or in a strictly positive oxidationstate, chosen from transition metals, lanthanides, actinides and metalsfrom Group IIIa, and of a ligand of this metal can, in addition,optionally be introduced into the reactor in stage (1′) and/or in stage(2′).

(D′) corresponds to the same characteristics and to the same preferencesas (D), this being the case whatever the degree of preference.

The radical polymerization process for the preparation of blockcopolymers according to the invention is advantageously carried out toprepare the block copolymers according to the invention.

Subsequently, a subject matter of the present invention is halogenatedpolymers which do not exhibit the disadvantages of the halogenatedpolymers of the prior art while retaining their advantages and which canin particular be obtained by the radical polymerization process for thepreparation of halogenated polymers described above.

To this end, the invention relates to halogenated polymers which have anumber-average molecular mass M_(n) of greater than 1.0×10⁴ and anM_(z)/M_(w) ratio of less than 1.65.

The distribution of the molecular masses of the halogenated polymersaccording to the invention is usually determined by steric exclusionchromatography, as clarified in example 1 of the present document.

From the distribution of the molecular masses thus obtained, it ispossible in particular to calculate:

-   -   the number-average molecular mass M_(n)=ΣN_(i)M_(i)/ΣN_(i),        where N_(i) is the number of moles of polymer with a molecular        mass of M_(i),    -   the weight-average molecular mass M_(w)=ΣN_(i)M_(i)        ²/ΣN_(i)M_(i),    -   the higher order average molecular mass M_(z)=ΣN_(i)M_(i)        ³/ΣN_(i)M_(i) ²,    -   the polydispersity index M_(w)/M_(n),    -   the M_(z)/M_(w) ratio.

The halogenated polymers according to the invention have anumber-average molecular mass M_(n) preferably of greater than 1.4×10⁴,particularly preferably of greater than 1.8×10⁴.

The halogenated polymers according to the invention have an M_(z)/M_(n)ratio preferably of less than 1.60.

In addition, the halogenated polymers according to the invention have apolydispersity index M_(w)/M_(n) advantageously of less than 2.00.

The halogenated polymers according to the invention can just as easilybe homopolymers of halogenated monomers as copolymers formed byhalogenated monomers with one another or with nonhalogenated monomers.They are preferably formed by at least 50 mol %, particularly preferablyby at least 80 mol % and very particularly preferably by 100% ofhalogenated monomers.

In addition, they are preferably polymers of halogenated vinyl monomers.Particularly preferably, they are chosen from polymers of chlorinatedvinyl monomers and polymers of fluorinated vinyl monomers.

Mention may be made, as examples of polymers of chlorinated vinylmonomers, of polymers of chlorinated vinyl monomers for which the numberof chlorine atoms is 1, polymers of chlorinated vinyl monomers for whichthe number of chlorine atoms is 2, trichloroethylene polymers,1,1,3-trichloropropene polymers and tetrachloroethylene polymers.

A first preferred family of polymers of chlorinated vinyl monomers iscomposed of polymers of chlorinated vinyl monomers for which the numberof chlorine atoms is 1. Mention may be made, as examples of suchpolymers, of allyl chloride polymers, crotyl chloride polymers and, witha very particular mention, vinyl chloride polymers.

The preferred vinyl chloride polymers have a polydispersity indexM_(w)/M_(n) advantageously of less than 1.60, preferably of less than1.50 and particularly preferably of less than 1.45. In addition, theyhave an M_(z)/M_(w) ratio preferably of less than 1.50.

A second preferred family of polymers of chlorinated vinyl monomers iscomposed of polymers of chlorinated vinyl monomers for which the numberof chlorine atoms is 2. Mention may be made, as examples of suchpolymers, of 1,1-dichloropropene polymers, 1,3-dichloropropene polymers,2,3-dichloropropene polymers and, with a very particular mention,vinylidene chloride polymers.

Mention may be made, as examples of polymers of fluorinated vinylmonomers, of chlorotrifluoroethylene polymers, trifluoroethylenepolymers, polymers of perfluorinated vinyl monomers, such astetrafluoroethylene polymers and hexafluoropropylene polymers, polymersof fluorinated vinyl monomers devoid of chlorine atoms and for which thenumber of fluorine atoms is 1, and polymers of fluorinated vinylmonomers devoid of chlorine atoms and for which the number of fluorineatoms is 2.

A first preferred family of polymers of fluorinated vinyl monomers iscomposed of polymers of fluorinated vinyl monomers devoid of chlorineatoms and for which the number of fluorine atoms is 1. Mention may bemade, as examples of such polymers, of allyl fluoride polymers and, witha very particular mention, vinyl fluoride polymers.

A second preferred family of polymers of fluorinated-vinyl monomers iscomposed of polymers of fluorinated vinyl monomers devoid of chlorineatoms and for which the number of fluorine atoms is 2. Mention may bemade, as examples of such polymers, of 3,3,3-trifluoropropene polymersand, with a very particular mention, vinylidene fluoride polymers.

The preferred vinylidene fluoride polymers have a polydispersity indexM_(w)/M_(n) advantageously of less than 1.85, preferably of less than1.75.

The halogenated polymers according to the invention can be in the formof liquids or of powders. Preferably, they are in the form of powders.

The halogenated polymers according to the invention have a whiteness,measured with a Minolta® CR 200 chromameter, advantageously having avalue of at least 80%, preferably of at least 85%. The measurement witha Minolta® CR 200 chromameter of the whiteness of the halogenatedpolymers according to the invention is carried out as clarified inexample 1 of the present document.

Subsequently, a final subject matter of the present invention isconsequently block copolymers, at least one block of which is ahalogenated polymer block, which exhibit numerous advantages and whichcan in particular be obtained by the radical polymerization process forthe preparation of block copolymers described above.

To this end, the invention relates to block copolymers, at least oneblock of which is a block of halogenated polymer identical to thehalogenated polymers described above ((CB₁) block copolymers).

It also relates to block copolymers, at least one block of which is ahalogenated polymer block, which have a number-average molecular massM_(n) of greater than 1.5×10⁴ and a polydispersity index M_(w)/M_(n) ofless than 1.60 ((CB₂) block copolymers).

Both for the (CB₁) block copolymers and for the (CB₂) block copolymersaccording to the present invention, the weight of the halogenatedpolymer block or blocks advantageously has a value of at least ½preferably of at least ⅓, of the weight of the block copolymersaccording to the invention. In addition, it advantageously has a valueof at most ⅘ of the weight of the (CB₁) and (CB₂) block copolymersaccording to the invention.

The (CB₁) and (CB₂) block copolymers according to the invention canoptionally comprise one or more blocks of nonhalogenated polymer.Mention may be made, as examples of such blocks, of blocks of styrenehomopolymers and blocks of random copolymers of styrene and ofacrylonitrile. Preferably, the block or blocks of nonhalogenated polymerare blocks of homopolymers.

Mention may be made, as examples of block copolymers according to theinvention, of the diblock copolymer composed of a block of a randomcopolymer of vinylidene chloride and of methyl acrylate and of a blockof a styrene homopolymer as manufactured according to example 7 of thepresent document.

Subsequently, a subject matter of the present invention is articles madeof halogenated polymer which do not exhibit the disadvantages of thearticles made of halogenated polymer of the prior art while retainingtheir advantages.

To this end, the invention relates to articles manufactured by using oneor more polymers chosen from the polymers prepared by the processes asdescribed above and the polymers as described above.

Mention may in particular be made, as examples of such articles, ofcompact layers, films, sheets, panels and profiles, tubes and pipes,mastics and cell layers.

These articles are usually manufactured conventionally by applying knownprocessing techniques, such as calendering, extrusion, injectionmolding, coating, spraying, dipping and molding.

There are many advantages to the radical polymerization processesaccording to the invention.

They have a well attested living nature, although employing halogenatedmonomers, such as vinyl chloride, vinylidene chloride, vinyl fluorideand vinylidene fluoride, regarded as intrinsically inclined to transferthe radical activity of the growing polymer chains onto themselves(reactions for transfer onto monomer) and/or onto dead polymer chains(reactions for transfer onto polymer).

Surprisingly, in the radical polymerization processes according to theinvention, a large number of polymer chains are (re)born at thebeginning of the polymerization and grow throughout the polymerization,without interruption or halting by transfer and/or disproportionationand/or recombination side reactions; the processes according to theinvention are thus distinguished with regard to the reaction mechanismfrom known radical polymerization processes.

From a macroscopic viewpoint, this is reflected in the fact that theradical polymerization processes according to the invention are suchthat, during the reaction, the number-average (or weight-average)molecular mass of the polymers continually increases when the fractionof halogenated monomer which has reacted increases, whereas it remainsvirtually constant throughout a “conventional” radical polymerization.

Another advantage of the radical polymerization processes according tothe invention, related to the above, is that the growth of the polymerchains of the halogenated polymers prepared by these processes can bereinitiated, bringing about the further reaction of the polymers, evenafter having been isolated from the polymerization medium, withethylenically unsaturated monomers identical to or different from thosewhich had been polymerized previously. In this way, it is possible toprepare block copolymers comprising at least one halogenated polymerblock. In contrast, it is usually impossible to synthesize suchcopolymers according to the “conventional” radical polymerizationprocess.

A final advantage of the radical polymerization processes according tothe invention is that they do not need to employ starting materialswhich are usually expensive, such as iodinated organic transfer agents.

The polymers according to the invention retain all the advantageouscharacteristic properties of the halogenated polymers of the prior art,in particular high chemical resistance to alkalis and to alcohols andhigh flame retardancy.

They have a polydispersity index M_(w)/M_(n) and an M_(z)/M_(w) ratiowhich are substantially reduced with respect to the polymers of theprior art.

In addition, they exhibit a number of other advantages related to theirlow polydispersity index. The main advantage is that the many propertiesof these polymers dependent on the molecular mass exhibit, at themolecular scale, an improved homogeneity with respect to the halogenatedpolymers of the prior art.

Because they are devoid of polymer chains of very low molecular mass,the halogenated polymers according to the invention have a greaterthermal stability than that of the halogenated polymers of the priorart; furthermore, the articles manufactured starting from these polymershave mechanical properties, in particular tensile strength, abrasionresistance and scratching resistance, which are better than those of thearticles manufactured starting from the halogenated polymers of theprior art.

Because they are devoid of polymer chains of very high molecular mass,the halogenated polymers according to the invention are employed in themolten state more easily than the halogenated polymers of the prior art;for the same reason, the plasticized articles manufactured starting fromthese polymers are better gelled and thus have mechanical properties, atransparency and a surface finish which are better than those of thearticles manufactured starting from the halogenated polymers of theprior art.

The examples which follow are intended to illustrate the inventionwithout, however, limiting the scope thereof.

EXAMPLE 1 According to the Invention

2000 g of demineralized water, 6 g of poly(vinyl alcohol) (dispersingagent), 1.5 g of molecular iodine and 1.5 g of diethyl peroxydicarbonate(radical-generating agent) were first of all introduced into a 3.5 ljacketed reactor equipped with a stirrer. The reactor was closed andthen the stirrer was started. A vacuum was applied in the reactor.

1000 g of vinyl chloride were introduced into the reactor.

The contents of the reactor were brought to 60° C. The moment at whichthe temperature of the contents of the reactor reached 60° C. is knownas t_(o). Reaction was allowed to take place.

At t_(o)+3 h 30, the reaction was halted by cooling the contents of thereactor (slurry) to ambient temperature as rapidly as possible.

The slurry was purified from unconverted vinyl chloride. The water wassubsequently removed therefrom by filtering and drying in a fluidizedbed. A poly(vinyl chloride) powder was thus obtained.

The fraction of vinyl chloride which has reacted (degree of conversion(f)), expressed as %, was calculated from the dry matter content of theslurry, itself determined by gravimetry.

The K value of the poly(vinyl chloride) was determined according tostandard ISO 1628-2.

The distribution of the molecular masses of the poly(vinyl chloride) wasalso determined by steric exclusion chromatography and the whiteness ofthe poly(vinyl chloride) was also determined using a Minolta CR® 200chromameter, as clarified below.

Determination of the Distribution of the Molecular Masses of a Polymer

The distribution of the molecular masses of the polymer was determinedusing a Waters® Alliance 2692 chromatograph equipped with a Shodex RI,model 2410, detector and with Waters® Styragel HR4, HR3 and HR2 columnsin series, using dimethylformamide additivated with LiBr as diluent at aconcentration of 0.1 mol/liter, at a flow rate of 1 ml/min and at atemperature of 40° C. The chromatograph had been calibrated beforehandusing poly(methyl methacrylate) standards, the Mark-Houwink factorsbeing α=0.770 and k=9.45×10⁻⁵.

Determination of the Whiteness of a Polymer

A Minolta CR® 200 chromameter equipped with a xenon arc lamp wasswitched on and the device was allowed to stabilize. The latter wasconfigured in colors, multimeasurements, channel 00 mode, with the Csource as illuminant. The channel 00 was subsequently calibrated usingan aluminum oxide standard tile. The polymer was poured into a measuringcup, provided for this purpose, until the cup slightly overflows, then aMatobel® glass sheet was placed over it and slight compression wasapplied so that the sheet comes into contact with the edge of the cup.The measuring head of the chromameter was subsequently placed on thesheet and 3 measurements (3 light flashes) of the Y, x, y coordinates ofthe CIE Lab 1931 space were performed consecutively. The mean thereofwas determined and then the trichromatic component Z=x×Y²/y²−Y and thewhiteness of the resin B=a×Z−b were calculated, a having a value of 0.9and b having a value of 1.085, a and b being empirical coefficientsdetermined beforehand experimentally so as to align the results obtainedaccording to the present measurement technique with those obtained usinga Photovolt® model 670 reflectometer.

EXAMPLE 2 According to the Invention

The preparation was carried out as in example 1, except that thereaction was halted at t_(o)+4 h (instead of t_(o)+3 h 30).

EXAMPLE 3 According to the Invention

The preparation was carried out as in example 1, except that thereaction was halted at t_(o)+5 h (instead of t_(o)+3 h 30).

The results of the various measurements of examples 1 to 3 are presentedin table 1.

TABLE 1 M_(n) M_(w) M_(z) Example f(%) Kv (×10⁴) (×10⁴) (×10⁴)M_(w)/M_(n) M_(z)/M_(w) B (%) 1 10 n.m. 2.0 2.6 3.5 1.30 1.35 n.m. 2 2243.1 2.0 2.8 3.9 1.40 1.39 85.0 3 33 44.8 2.4 3.4 4.8 1.42 1.41 87.3n.m. = not measured

EXAMPLE 4 Comparative Example

The distribution of the molecular masses of commercial vinyl chloridehomopolymers was determined using a Waters® Alliance 2692 chromatographunder exactly the same conditions as those applied in examples 1 to 3.

The results of the measurements of example 4 are presented in table 2

TABLE 2 M_(n) M_(w) M_(z) Resin Kv (×10⁴) (×10⁴) (×10⁴) M_(w)/M_(n)M_(z)/M_(w) PVC, Solvin ® 266RC 66.0 4.8 9.6 16.2 2.00 1.69 PVC,Solvin ® 275PC 74.8 6.1 12.6 21.3 2.07 1.69

EXAMPLE 5 According to the Invention

2429 g of demineralized water, a methylhydroxypropylcellulose dispersingagent, in a proportion of 0.04 g per 100 g of monomer, and 4.1 g (0.016mol) of molecular iodine were successively introduced into a 4 literjacketed reactor equipped with a stirrer of turbine type rotating at 880revolutions/minute. A vacuum was applied 13.4 g of tert-amyl perpivalatewere introduced. After having waited 5 minutes, 609 g (4.06 mol) ofhexafluoropropylene and 644 g (10.06 mol) of vinylidene fluoride weresuccessively charged to the reactor. The contents of the reactor weregradually heated until the latter had reached the stationary temperatureof 60° C. 614 g (9.59 mol) of vinylidene fluoride were graduallyinjected into the reactor, so as to keep the pressure constant thereinat a value of 120 bar. Subsequently, the pressure in the reactor wasallowed to gradually fall until it had reached 100 bar. The contents ofthe reactor were then heated to 65° C. When the pressure in the reactorhad reached 60 bar, i.e. 597 min after having reached the stationarytemperature of 60° C., the aqueous suspension was degassed (by loweringthe pressure to atmospheric pressure). The copolymer was subsequentlycollected by filtration and then it was resuspended in clean water in avessel with stirring. After a washing cycle, the polymer was dried in anoven to constant weight.

The fraction by weight of hexafluoropropylene and of vinylidene fluoridewhich had been consumed overall by the reaction was determined: this was67%.

Furthermore, the distribution of the molecular masses of the copolymerthus prepared was determined using a Waters® Alliance 2692 chromatographunder exactly the same conditions as those applied in examples 1 to 3.The following were obtained:M _(n)=7.7×10⁴ , M _(w)=13.0×10⁴ , M _(z)=20.6×10⁴ , M _(w) /M _(n)=1.69and M _(z) /M _(w)=1.58.

EXAMPLE 6 Comparative Example

The preparation was carried out as in example 5, except that iodine wasnot introduced into the reactor.

The pressure in the reactor had reached 60 bar 261 min after havingreached the stationary temperature of 60° C.

The fraction by weight of hexafluoropropylene and of vinylidene fluoridewhich had been consumed overall by the reaction was determined: this was73%.

Furthermore, the distribution of the molecular masses of the copolymerthus prepared was determined using a Waters® Alliance 2692 chromatographunder exactly the same conditions as those applied in example 5. Thefollowing were obtained:M _(n)=9.5×10⁴ , M _(w)=20.9×10⁴ , M _(z)=41.4×10⁴ , M _(w) /M _(n)=2.20and M _(z) /M _(w)=1.98.

EXAMPLE 7 According to the Invention

A vacuum was applied in a 300 ml glass reactor. A first solution,composed of 64.8 g of vinylidene chloride, 14.4 g of methyl acrylate,1.006 g of molecular iodine and 88 g of benzene, was subsequentlyintroduced therein and then a second solution, composed of 0.975 g ofazobisisobutyronitrile and 10 g of benzene, was subsequently introducedtherein.

Immediately after having introduced the second solution into thereactor, the latter was placed in a bath thermostatically controlled at70° C. The moment at which the temperature of the contents of thereactor reached 70° C. is t_(o). Reaction was allowed to take place.

At t_(o)+30 hours, the reaction was halted by cooling the contents ofthe reactor to ambient temperature as rapidly as possible (intermediatesolution (S1)).

(S1) essentially comprise a copolymer of vinylidene chloride and ofmethyl acrylate (intermediate polymer (P1)) and unconverted vinylidenechloride and methyl acrylate, in solution in benzene.

The polymer (P1) included in the intermediate solution (S1) wasprecipitated from methanol for approximately 72 hours and was thenfiltered off and dried in an oven under vacuum (intermediate polymer(P′1)).

6.01 g of styrene and 2.43 g of polymer (P′1) were introduced into a 25ml glass reactor. A vacuum was applied.

The reactor was subsequently placed in a bath thermostaticallycontrolled at 110° C. The moment at which the temperature of thecontents of the reactor reached 110° C. is t₁. Reaction was allowed totake place.

At t₁+5 h 45, the reaction was halted by cooling the contents of thereactor to ambient temperature as rapidly as possible (finalsolution/bulk (S2)).

(S2) essentially comprised a block copolymer comprising a block of acopolymer of vinylidene chloride and of methyl acrylate and apolystyrene block (block copolymer (P2)), and unconverted styrene.

Starting from a sample of (S2), the distribution of the molecular massesof the block copolymer (P2) was determined by steric exclusionchromatography.

The following results relating to the distribution of the molecularmasses of (P2) were obtained: M_(n)=2.0×10⁴, M_(z)=4.3×10⁴ andM_(w)/M_(n)=1.58.

1. A radical polymerization process for the preparation of a blockcopolymer, at least one block of which is a polymer of fluorinated vinylmonomer or monomers block, comprising: reacting (A′) one or moreethylenically unsaturated monomers, and (B′) one or more polymers of afluorinated vinyl monomer or monomers, or a precursor block copolymer,wherein (1′) all or optionally a fraction of (A′) and all or optionallya fraction of (B′) are introduced into a reactor, then (2′) the contentsof the reactor are reacted, while introducing therein the optionalbalance of (A′) and the optional balance of (B′) and the reaction isbrought to an end, wherein the precursor block copolymer is prepared byreacting one or more ethylenically unsaturated monomers and one or morepolymers of fluorinated vinyl monomer or monomers wherein said polymerof fluorinated vinyl monomer or monomers is a polymer prepared by aprocess employing (A) one or more ethylenically unsaturated monomers, atleast one of which is a fluorinated vinyl monomer (B) molecular iodine,and (C) one or more radical-generating agents selected from the groupconsisting of a diazo compound, a peroxide and a dialkyldiphenylalkane;which comprises the stages according to which (1) at least a fraction ofeach of the compounds (A), (B) and (C) is introduced into a reactor,then (2) the contents of the reactor are reacted, while introducingtherein the optional balance of each of the compounds (A), (B) and (C)and the reaction is brought to an end.
 2. The process as claimed inclaim 1, wherein at least 50 mol % of (A) are one or more ethylenicallyunsaturated fluorinated vinyl monomers.
 3. The process as claimed inclaim 1, wherein the ethylenically unsaturated monomer or one of theethylenically unsaturated monomers is vinylidene fluoride.
 4. Theprocess as claimed in claim 1, wherein (A) is comprised of a singleethylenically unsaturated monomer which is a fluorinated vinyl monomer,at least 50 mol % of (A) being introduced into the reactor in stage (1).5. The process as claimed in claim 1, wherein (A) is comprised of aplurality of ethylenically unsaturated monomers, the ethylenicallyunsaturated monomers constituting (A) being introduced into the reactoraccording to the same introduction policy.
 6. The process as claimed inclaim 1, wherein (A) is comprised of at least a first unsaturatedmonomer and a second ethylenically unsaturated monomer, the firstethylenically unsaturated monomer comprised in (A) introduced into thereactor in stage (1), the second ethylenically unsaturated monomer ormonomers comprised in (A) introduced into the reactor in stage (2), inas many times as the number of ethylenically unsaturated monomersconstituting (A) minus 1, one after the other, each new introduction ofan ethylenically unsaturated monomer into the reactor in stage (2) beingcarried out only after the ethylenically unsaturated monomer or monomerspreviously introduced into the reactor has each reacted up to at least50 mol %.
 7. The process as claimed in claim 1, wherein (A) is comprisedof at least a first unsaturated monomer and a second ethylenicallyunsaturated monomer, the first ethylenically unsaturated monomercomprised in (A) introduced into the reactor in stage (1), all or afraction of the second ethylenically unsaturated monomer or monomerscomprised in (A) introduced gradually into the reactor in stage (2). 8.The process as claimed in claim 1, wherein the number of moles of (B)with respect to the number of moles of (A) has a value of at least2.5×10⁻⁵.
 9. The process as claimed in claim 1, wherein at least 50 mol% of (B) are introduced into the reactor in stage (1).
 10. The processas claimed in claim 1, wherein the number of moles of (C) with respectto the number of moles of (B) has a value of at least
 1. 11. The processas claimed in claim 1, wherein one or more complexes of a metal, in the0 oxidation state or in a strictly positive oxidation state, selectedfrom the group consisting of a transition metal, a lanthanide, anactinide, and a metal from Group IIIa, and of a ligand of this metal isadditionally introduced into the reactor, in at least one of stage (1)and stage (2).
 12. The process as claimed in claim 1, wherein thecontents of the reactor, in stage (1) and in stage (2), are devoid ofany complex of a metal, in the 0 oxidation state or in a strictlypositive oxidation state, selected from the group consisting of atransition metal, a lanthanide, an actinide and a metal from Group IIIa,and of a ligand of this metal.
 13. A block copolymer comprising at leastone block of a polymer of fluorinated vinyl monomer or monomers having anumber-average molecular mass M_(n) of greater than 1.0×10⁴ and anM_(z)/M_(w) ratio of less than 1.65.
 14. A block copolymer comprising atleast one block of a polymer of fluorinated vinyl monomer or monomers,which has a number-average molecular mass M_(n) of greater than 1.4×10⁴and a polydispersity index M_(w)/M_(n) of less than 1.85.
 15. An articlemanufactured by using one or more block copolymers prepared by theprocess as claimed in claim
 1. 16. An article manufactured by using oneor more block copolymers as claimed in claim
 13. 17. An articlemanufactured by using one or more block copolymers as claimed in claim14.